Rock-drill.



G. R. BENNETT.

ROCK DRILL.

APPLICATION FILED OCT. 15, 1912.

m m, Q W IE M w w n w m n M III I H .m l dfi sg M m N. G P v m E Q m 8 u w W E z. w -HQUH. W M 1 k w AX 0 N 4 iinrrnn srATEs PATENT OFFICE.

enonen R. BENNETT, or DENVERQCOLORADO.

Specification of Letters Patent.

ROCK-DRILL.

Patented May 23, 1916.

Application filed October 15, 1912. Serial No. 725,820.

My invention relates to improvements in rock drills and its object resides in the provision of .an engine ofthis class in the operation of which, a rapid succession of blows is effectively delivered upon a cutting tool by the cooperative actions of a mechanical agent and a motive fluid such as air under compression.

An embodiment of my invention is illustrated in the accompanying drawings in the variousviews of which like parts are similarly designated and in which,

Figure 1 represents a side elevation of the improved rock drill, Fig. 2 a longitudinal section of the same drawn to an enlarged scale with the parts in the position they occupy when the reciprocatingpiston included in the construction, has reached the end of' its forward stroke, Fig. 3 a similar view with the moving parts in their positions at the termination of the rearward movement of the piston, and Fig. 4 a cross-section taken along the line H, Fig. 2.

Referring to the drawings by numerals, 2 designates a cylindrical housing supported on a suitable base 3 and provided at its rear end with a stuffing box 4 for the support and impervious guidance of the rod 5 of a reciprocating piston 6 which is slidably fittedin the housing. The latter has at its forward end an axially alined sleeve 7 for the support of a cutting tool 8 whose shank projects into the interior of the housing to be driven forwardly by the impact of a reciprocating hammer as will hereinafter be described. The housing 2 has furthermore, at its forward end a plurality of ports 9 for the admission of air under atmospheric pres sure to its interior, and a conduit 10 connects an opening at its opposite end with a source of motive fluid such as air under compression. The rearward portion of the housing is, interiorly, increased in diameter to re ceive an internally, longitudinally fluted bushing 12 which serves to provide a plurality of longitudinal channels 13 which, when the piston has reached the end of its rearward stroke, establish communication between the portions of the housing at oppo-- site sides thereof. a I

The hammer 18 which in the operation of the drillimpinges upon the end of the tool 8, is slidably fitted in the housing between the forward end thereof and the reciprocating piston to be actuated by the motive fluid which flows through the channels past the piston when the latter reaches the end of its rearward stroke. The piston 6 is provided with an internal valve chamber 1 1 which has an opening in the forward face thereof and which is in continuous communicatlon with its opposite face by a plurality of passages 15. A check-valve 16 which is normally held against its seat by a coiled spring 17 is arranged to open for the escape of compressed air from the space between the hammer 18 and the piston, during forward movement of the latter after the hammer has delivered a blow upon the tool at the forward end of the housing. The pistonrod 5 is connected at itsprotruding extremity with a mechanism of suitable construction adapted to impart 'a reciprocating movement to the piston, as, for example, the

in continuous communication with a source of motive fluid by means of the conduit 10, or a check-valve 21 may be applied as is shown in Fig. 3, to interrupt the returnflow of fluid to the source of supply, when during rearward movement of the piston the air contained in the housing is over-compressed. Assuming that both the hammer 18 and the piston 6 are at the end of their forward movement in the position shown in Fig. 2, power is applied to the crank-shaft to draw the piston rearwardly. Inasmuch as the hammer and the piston are closely fitted in the cylinder, the rearward movement of the piston will tend to create a partial vacuum between them with the result that the hammeris compelled to follow the piston in its rearward movement by pressure of the air admitted into the housing through the ports 9 at the forward end thereof. These corresponding movements of the two reciprocating elements will continue until the piston on reaching the end of its rearward stroke, uncovers the ends of the chem-- nels 13, when the compressed-air contained in the rearward portion of the housing, escapesinto the space between the piston and the hammer, to drive the latter forwardly against the extremity of the drilling-tool 8;

During the subsequent forward movement of the piston, the body of fluid by which the hammer was impelled, is forced .past the check-valve 16, into the rearward portion of the housing until the piston has again 7 its opposite end faces, a valve arranged in said chamber providing for a rearward flow of fluid therethrough, a second piston intermediate the first referred to piston and said tool, said cylinder having air-inlet ports at its forward end and said longitudinal channels communicating with the space between the pistons and the space at the rear of the first referred to piston when the latter piston reaches a predetermined point in its travel. i

2. The combination of a rear end closed cylinder, the rear portion of the chamber of said cylinder being increased diametrically, said rear diametrical chamber having a bushing provided with a plurality of longitudinal channels, a longitudinally movable tool arranged at the forward end of said cylinder, a piston arranged within the rearward end of said cylinder and having a springcontrolled valve arranged within a chamber thereof, said piston also having a plural ity of passages communicating with said chamber and opening through the rear end of the piston, a second piston intermediate said tool and the first referred to piston, said cylinder having air-inlet ports at its forward end and said longitudinal channels communicating with the space between the pistons and the space at the rear of the first referred to piston whenthe latter piston reaches a predetermined point in its travel. Intestimony whereof I have affixed my signature in presence of two witnesses.

GEORGE RfBENNETT.

Witnesses I G. J. ROLLANDET, L. RHoADEs.

copies of this patent may he obtained for five cents each, by addressing the Commissioner of 'Patents 7 Washington, D. 0." 

